Plaque fluid and saliva was collected from 25 children aged 7-12 years from two communities with contrasting levels of caries (DMFS 1 v DMFS 39). The samples were assayed for SIgA, IgG, IgM, the third component of complement (C'3, lactoferrin, lactoperoxidase, lysozyme, albumin and total protein. With the exception of lactoperoxidase and IgG the levels of the specific proteins were significantly higher in plaque fluid than in saliva. However, no significant differences were detected between the communities in either plaque fluid or saliva.